1. Technical Field
The present invention relates to image reading apparatuses that read an image on a target object by causing a reading portion to move along the target object.
2. Related Art
Heretofore, as an example of image reading apparatuses, an image reading apparatus provided with a transparent plate that allows a document to be mounted thereon has been well known (for example, JP-A-2012-63521). In this image reading apparatus, an image on a target object, such as a document, is read via such a transparent plate by allowing the target object to be mounted on one side face of the transparent plate and simultaneously therewith causing a slider (a reading portion) to move at the other side face of the transparent plate.
Further, in such an image reading apparatus, the slider moves on the basis of driving by a motor (a driving source).
Thus, in an image reading apparatus disclosed in JP-A-2012-63521, when an ambient temperature value measured by using a temperature sensor is smaller than or equal to a predetermined value, the movement speed of the slider that is caused to move and read an image is made low. That is, the possibility in that the motor enters the step-out state is reduced by making a torque required to cause the slider to move correctly small. In such an image reading apparatus, however, for example, in conjunction with lowering of ambient temperature, a torque output by the motor decreases, but in contrast, a load applied to the motor that causes the slider to move increases due to the increase of the viscosity of a lubricant agent, and the like. For this reason, there sometimes occurs a case where the motor enters a step-out state as a result of the increase of the load applied to the motor in contrast to the decrease of the torque output by the motor.
By the way, in such an image reading apparatus, image data is generated by, simultaneously with causing a slider to move, continuously reading an amount of light received per unit time as one of pieces of data representing an image, and combining the pieces of data. Thus, when the movement speed of the slider is made low, an amount of the pieces of data that are read increases and, as a result, the size of the image data that are generated also increases.
In addition, this problem is not limited to image reading apparatuses that read an image on a target object by causing the slider to move, but has become substantially common to image reading apparatuses that read an image on a target object by causing a reading portion to move.